Organic electroluminescent element, display device and lighting device

ABSTRACT

Disclosed is an organic electroluminescent device having long life, while exhibiting high luminous efficiency. Also disclosed are an illuminating device and a display, each using such an organic electroluminescent device. In the organic electroluminescent device, a compound represented by the general formula (A) which is suitable as a host material for a phosphorescent metal complex is used at least in one sublayer of a light-emitting layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 12/443,410 filed on Mar. 27, 2009, the entirecontents of which are incorporated herein by reference. Ser. No.12/443,410 is the U.S. national stage of application No.PCT/JP2007/073777, filed on Dec. 10, 2007. Priority under 35 U.S.C.§119(a) and 35U.S.C. §365(b) is hereby claimed from Japanese PatentApplication No. 2006- 335664, filed Dec. 13, 2006, and the contents ofwhich are also incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent element,a display device and a lighting device.

BACKGROUND

Conventionally, an emission type electronic display device includes anelectroluminescence display (hereinafter, referred to as an ELD). Aconstituent element of an ELD includes such as an inorganicelectroluminescent element and an organic electroluminescent element(hereinafter, referred to as an organic EL element). An inorganicelectroluminescent element has been utilized as a flat light source,however, it requires a high voltage of alternating current to operate anemission element. An organic electroluminescent element is an elementprovided with a constitution comprising an emitting layer containing aemitting substance being sandwiched with a cathode and an anode, and anexciton is generated by an electron and a positive hole being injectedinto the emitting layer to be recombined, resulting emission utilizinglight release (fluorescence·phosphorescence) at the time of deactivationof said exciton; the emission is possible at a voltage of approximatelya few to a few tens volts, and an organic electroluminescent element isattracting attention with respect to such as superior viewing angle andhigh visual recognition due to a self-emission type as well as spacesaving and portability due to a completely solid element of a thin layertype.

However, in an organic electroluminescence in view of the futurepractical application, desired has been development of an organic ELelement which efficiently emits at a high luminance with a low electricconsumption.

In Japanese Patent No. 3093796, a slight amount of a fluorescentsubstance has been doped in a stilbene derivative, distyrylarylenederivative or a tristyrylarylene derivative, to achieve improvedemission luminance and a prolonged lifetime of an element.

Further, there are known such as an element having an organic emittinglayer comprising a 8-hydroxyquinoline aluminum complex as a hostcompound which is doped with a slight amount of a fluorescent substance(for example, JP-A 63-264692) and an element having an organic emittinglayer comprising a 8-hydroxyquinoline aluminum complex as a hostcompound which is doped with quinacridone type dye (for example, JP-A3-255190).

In the case of utilizing emission from an excited singlet as describedabove, since a generation ratio of a singlet exciton to a tripletexciton is 1/3, that is, a generation probability of an emitting excitonspecies is 25% and a light taking out efficiency is approximately 20%,the limit of an external quantum efficiency (ηext) of taking out lightis said to be 5%.

However, since an organic EL element which utilizes phosphorescence froman excited triplet has been reported from Princeton University (M. A.Baldo et al., Nature vol. 395, pp. 151-154 (1998)), researches onmaterials exhibiting phosphorescence at room temperature have come to beactive.

For example, it is also disclosed in A. Baldo et al., Nature, vol. 403,No. 17, pp. 750-753 (2000), and U.S. Pat. No. 6,097,147.

Since the upper limit of internal quantum efficiency becomes 100% byutilization of an excited triplet, which is principally 4 times of thecase of an excited singlet, it may be possible to achieve almost thesame ability as a cooled cathode ray tube to attract attention also foran illumination application.

For example, in such as S. Lamansky et al., J. Am. Chem. Soc., vol. 123,p. 4304 (2001), many compounds mainly belonging to heavy metal complexessuch as iridium complexes have been synthesized and studied.

Further, in the aforesaid, A. Baldo et al., Nature, vol. 403, No. 17,pp. 750-753 (2000), utilization of tris(2-phenylpyridine)iridium as adopant has been studied.

In addition to these, M. E. Tompson et al., at The 10th InternationalWorkshops on Inorganic and Organic Electroluminescence (EL'00,Hamamatsu), have studied to utilize L₂Ir(acac) such as (ppy)₂Ir(acac) asa dopant, Moon-Jae Youn. Og., Tetsuo Tsutsui et al., also at The 10thInternational Workshops on Inorganic and Organic Electroluminescence(EL'00, Hamamatsu), have studied utilization of such astris(2-(p-tolyl)pyridine)iridium (Ir(ptpy)₃) andtris(benzo[h]quinoline)iridium (Ir(bzq)₃) (herein, these metal complexesare generally referred to as orthometalated iridium complexes.).

Further, in also the aforesaid, S. Lamansky et al., J. Am. Chem. Soc.,vol. 123, p. 4304 (2001), studies have been carried out to prepare anelement utilizing various types of iridium complexes.

Further, to obtain high emission efficiency, Ikai et al., at The 10thInternational Workshops on Inorganic and Organic Electroluminescence(EL'00, Hamamatsu) utilized a hole transporting compound as a host of aphosphorescent compound. Further, M. E. Tompson et al. utilized varioustypes of electron transporting materials as a host of a phosphorescentcompound doped with a new iridium complex. An orthometalated complexprovided with platinum instead of iridium as a center metal is alsoattracting attention. With respect to these types of complexes, manyexamples having a characteristic ligand are known (for example, refer toPatent Documents 1-5 and Non-Patent Document 1.).

In any case, emission luminance and emission efficiency aresignificantly improved compared to conventional elements because theemitting light arises from phosphorescence, however, there has been aproblem of a poor emission lifetime of the element compared toconventional elements. It is hard to achieve an emission of a shortwavelength and an improvement of an emission lifetime of the element fora phosphorescent emission material provided with a high efficiency. Atpresent state, it cannot be achieved a level of a practical use.

In order to improve the above-described defects, there are known an Ircomplex and a Pt complex having a phenylimidazole ligand (for example,refer to Patent Documents 6-7). However, the emission efficiency and theemission lifetime are still not fully satisfied, and further improvementin emission efficiency and emission lifetime are demanded.

[Patent Document 1] JP-A 2002-332291

[Patent Document 2] JP-A 2002-332292

[Patent Document 3] JP-A 2002-338588

[Patent Document 4] JP-A 2002-226495

[Patent Document 5] JP-A 2002-234894

[Patent Document 6] WO 02/15645

[Patent Document 7] WO 05/7767

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide an organic EL elementmaterial which has high emission efficiency and long emission lifetime,a lighting device and a display device.

Means to Solve the Problems

An object of the present invention described above has been achieved bythe following constitutions.

-   1. An organic electroluminescent element comprising a substrate    having thereon at least an anode and a cathode, and a light emitting    layer between the aforesaid anode and the aforesaid cathode, wherein    at least one light emitting layer incorporates a compound    represented by Formula (A):

wherein A1 and A2 each represents a hydrogen atom or a substituent,provided that at least one of A1 and A2 is a substituent; X and Y eachrepresents O, S, Se, Te, or N—R (where R represents a hydrogen atom or asubstituent); L1, L2, and L3 each represents a divalent linking group; nrepresents an integer of at least 1; n1 and n2 each represents aninteger of at least 0; and n3 and n4 each represents 0 or 1, providedthat the following condition is satisfied, n1+n2≧2.

-   2. The organic electroluminescent element, described in the    above-mentioned item 1, wherein the aforesaid L3 represents an    arylene group, a heteroarylene group, a divalent heterocyclic group    or an alkylene group.-   3. The organic electroluminescent element, described in the    above-mentioned item 1, wherein the aforesaid L3 represents an    arylene group.-   4. The organic electroluminescent element, described in the    above-mentioned item 1, wherein the aforesaid L3 represents a    m-phenylene group.-   5. The organic electroluminescent element, described in any one of    the above-mentioned items 1-4, wherein the aforesaid n1 represents 1    or 2.-   6. The organic electroluminescent element, described in any one of    the above-mentioned items 1-5, wherein the aforesaid n2 represents 1    or 2.-   7. The organic electroluminescent element, described in any one of    the above-mentioned items 1-6, wherein the aforesaid n represents 1    or 2.-   8. The organic electroluminescent element, described in any one of    the above-mentioned items 1-7, wherein at least one of the aforesaid    A1 and A2 represents a nitrogen atom-containing substituent.-   9. The organic electroluminescent element, described in the    above-mentioned item 8, wherein the aforesaid nitrogen    atom-containing substituent is a carbazolyl group.-   10. The organic electroluminescent element, described in the    above-mentioned item 8, wherein the aforesaid nitrogen    atom-containing substituent represents a carbolynyl group and the    aforesaid carbolynyl group is the substituent which is derived from    the carboline derivative represented by Formula (a):

wherein X₁-X₈ each represents a nitrogen atom or —C(Ra)═; at least oneof the aforesaid X₁-X₈ represents a nitrogen atom; and Ra and Rb eachrepresents a hydrogen atom or a substituent.

-   11. The organic electroluminescent element, described in the    above-mentioned item 8, wherein the aforesaid nitrogen    atom-containing substituent is a diarylamino group.-   12. The organic electroluminescent element, described in any one of    the above-mentioned items 1-11, wherein the aforesaid X is an oxygen    atom.-   13. The organic electroluminescent element, described in any one of    the above-mentioned items 1-12, wherein the aforesaid light emitting    layer incorporates a phosphorescence emitting metal complex.-   14. The organic electroluminescent element, described in the    above-mentioned item 13, wherein the aforesaid phosphorescence    emitting metal complex is an Ir complex.-   15. The organic electroluminescent element, described in the    above-mentioned items 13 or 14, wherein the aforesaid    phosphorescence emitting metal complex is represented by Formula    (B):

wherein R₁ represents a substituent; Z represents a group of metal atomsnecessary for forming a 5-7 membered ring; n₁ represents an integer of0-5; B₁-B₅ each represents a carbon atom, a nitrogen atom, an oxygenatom, or a sulfur atom and at least one represents a nitrogen atom; M₁represents a metal of Groups 8-10 in the element periodic table; X₁ andX₂ each represents a carbon atom, a nitrogen atom, or an oxygen atom; L₁represents a group of atoms which form a bidentate ligand with X₁ andX₂; m1 represents 1, 2, or 3; and m2 represents 0, 1, or 2, providedthat a sum of m1 and m2 is 2 or 3.

-   16. The organic electroluminescent element, described in any one of    the above-mentioned items 1-15, wherein m2 of the phosphorescence    emitting metal complex represented by the aforesaid Formula (B) is    0.-   17. The organic electroluminescent element, described in the    above-mentioned items 15 or 16, wherein a nitrogen-containing    heterocyclic ring formed by phosphorescence emitting metal complexes    B₁-B₅ represented by the aforesaid Formula (B) is an imidazole ring.-   18. The organic electroluminescent element, described in any one of    the above-mentioned items 1-17, emitting white light.-   19. A display device provided with the organic electroluminescent    element described in any one of the above-mentioned items 1-18.-   20. An illuminating device provided with the organic    electroluminescent element described in any one of the    above-mentioned items 1-18.

Effects of the Invention

The present invention has enabled to provide an organic EL element, alighting device and a display device having high emission efficiency andlong emission lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing to show an example of a display deviceconstituted of an organic EL element.

FIG. 2 is a schematic drawing of display section.

FIG. 3 is a schematic drawing of a lighting device.

FIG. 4 is a schematic cross-sectional view of a lighting device.

DESCRIPTION OF SYMBOLS

1 display

3 pixel

5 scanning line

6 data line

A display section

B control section

101 organic EL element

107 glass substrate having a transparent electrode

106 organic EL layer

105 cathode

102 glass cover

108 nitrogen gas

109 desiccant

BEST MODES TO CARRY OUT THE INVENTION

In the organic EL element of the present invention, by using any one ofthe aforementioned embodiments of items 1-18, there has been provided anorganic EL element exhibiting high emission taking out quantumefficiency and having a prolonged emission lifetime. And further, alighting equipment and a display device pf high luminance can besuccessfully provided.

Each of the constituent elements of the present invention will now bedetailed successively.

<Constituting Layers of Organic EL Element>

Specific examples of a preferable layer constitution of an organic ELelement of the present invention are shown below; however, the presentinvention is not limited thereto.

-   (i) anode/light emitting layer/electron transport layer/cathode-   (ii) anode/positive hole transport layer/light emitting    layer/electron transport layer/cathode-   (iii) anode/positive hole transport layer/light emitting    layer/positive hole inhibition layer/electron transport    layer/cathode-   (iv) anode/positive hole transport layer/light emitting    layer/positive hole inhibition layer/electron transport    layer/cathode buffer layer/cathode-   (v) anode/anode buffer layer/positive hole transport layer/light    emitting layer/positive hole inhibition layer/electron transport    layer/cathode buffer layer/cathode

In the organic EL element of the present invention, the maximumwavelength of light emitted from the blue light emitting layer ispreferably within 430-480 nm, and the green light emitting layer ispreferably a monochromatic light emitting layer which results in themaximum wavelength of the emitted light within 510-550 nm, while the redlight emitting layer is a monochromatic light emitting layer whichresults in the maximum wavelength of the emitted light in the range of600-640 nm. Display devices employing these are preferred. Further, awhile light emitting layer is acceptable, which is prepared bylaminating at least three of these layers. Further, between the lightemitting layers may be present a non-light emitting intermediate layer.As the organic EL element of the present invention, preferred is a whitelight emitting layer, and illuminating devices employing these arepreferred.

Each of the layers which constitute the organic EL elements of thepresent invention will now be sequentially detailed.

<Emitting Layer>

The emitting layer of the present invention is a layer, which emitslight via recombination of electrons and positive holes injected from anelectrode or a layer such as an electron transport layer or a positivehole transport layer. The emission portion may be present either withinthe emitting layer or at the interface between the emitting layer and anadjacent layer thereof.

The total thickness of the light emitting layer is not particularlylimited. However, in view of the layer homogeneity, the minimization ofapplication of unnecessary high voltage during light emission, and thestability enhancement of the emitted light color against the driveelectric current, the layer thickness is regulated preferably in therange of 2 nm-5 μm, more preferably in the range of 2 nm-200 nm, butmost preferably in the range of 10-20 nm.

With regard to preparation of the light emitting layer, light emittingdopants and host compounds, described below, may be subjected to filmformation via a conventional thin filming method such as a vacuumdeposition method, a spin coating method, a casting method, an LBmethod, or an ink-jet method.

It is preferable that the light emitting layer of the organic EL elementof the present invention incorporates host compounds and at least onekind of light emitting dopants (also referred to as phosphorescencedopants or phosphorescence emitting dopants) and fluorescence dopants.(Host Compounds (also referred to as light emitting hosts)

Host compounds employed in the present invention will now be described.

“Host compounds”, as described in the present invention, are defined ascompounds, incorporated in a light emitting layer, which result in aweight ratio of at least 20% in the above layer and also result in aphosphorescent quantum yield of the phosphorescence emission of lessthan 0.1. Further, of compounds incorporated in the light emittinglayer, it is preferable that the weight ratio in the aforesaid layer isat least 20%.

<<Compounds Represented by Formula (A)>>

Compounds represented by Formula (A) will be described.

Compounds represented by Formula (A) according to the present inventionare incorporated in the light emitting layer of the organic EL elementof the present invention. It is preferable that the compoundsrepresented by the aforesaid Formula (A) are employed as a host compoundin the light emitting layer.

In Formula (A), examples of the substituents represented by A1 and A2each include: an alkyl group (for example, a methyl group, an ethylgroup, a propyl group, an isopropyl group, a tert-butyl group, a pentylgroup, a hexyl group, an octyl group, a dodecyl group, a tridecyl group,a tetradecyl group, and a pentadecyl group); a cycloalkyl group (forexample, a cyclopentyl group, and a cyclohexyl group); an alkenyl group(for example, a vinyl group, an allyl group, a 1-propenyl group, a2-butenyl group, a 1,3-butadienyl group, a 2-pentenyl group, and anisopropenyl group); an alkynyl group (for example, an ethynyl group anda propargyl group); an aromatic hydrocarbon ring group (also called anaromatic carbon ring or an aryl group, for example, a phenyl group, ap-chlorophenyl group, a mesityl group, a tolyl group, a xylyl group, anaphthyl group, an anthryl group, an azulenyl group, an acenaphthenylgroup, a fluorenyl group, a phenantolyl group, an indenyl group, apyrenyl group, and a biphenyryl group); an aromatic heterocyclic group(for example, a furyl group, a thienyl group, a pyridyl group, apyridazinyl group, a pyrimidinyl group, a pyrazinyl group, a triazinylgroup, an imidazolyl group, a pyrazolyl group, a thiazolyl group, aquinazolinyl group, a carbazolyl group, a carbolynyl group; adiazacarbazolyl group (which is a group in which one of the carbon atomsconstituting the carboline ring of the above carbolynyl group isreplaced with a nitrogen atom), a phtharadinyl group; a heterocyclicgroup (for example, a pyrrolidyl group, an imidazolidyl group, amorpholyl group, and an oxazilidyl group); an alkoxyl group (forexample, a methoxy group, an ethoxy group, a propyloxy group, apentyloxy group, an hexyloxy group, an octyloxy group, and a dodecyloxygroup); a cycloalkoxy group (for example, a cyclopentyloxy group and acyclohexyloxy group); an aryloxy group (for example, a phenoxy group anda naphthyloxy group); an alkylthio group (for example, a methylthiogroup, an ethylthio group, a propylthio group, a pentylthio group, ahexylthio group, an octylthio group, and a dodecylthio group); acycloalkylthio group (for example, a cyclopentylthio group and acyclohexylthio group); an arylthio group (for example, a phenylthiogroup and a naphthylthio group); an alkoxycarbonyl group (for example, amethyloxycarbonyl group, an ethyloxycarbonyl group, a butyloxycarbonylgroup, an octyloxycarbonyl group, and a dodecyloxycarbonyl group); anaryloxycarbonyl group (for example, a phenyloxycarbonyl group and anaphthyloxycarbonyl group); a sulfamoyl group (for example, anaminosulfonyl group, a methylaminosulfonyl group, adimethylaminosulfonyl group, a butylaminosulfonyl group, ahexylaminosulfonyl group, a cyclohexylaminosulfonyl group, anoctylaminosulfonyl group, a dodecylaminosulfonyl group, aphenylaminosulfonyl group, a naphthylaminosulfonyl group, and a2-pyridylaminosulfonyl group); an acyl group (for example, an acetylgroup, an ethylcarbonyl group, a propylcarbonyl group, a pentylcarbonylgroup, a cyclohexylcarbonyl group, an octylcarbonyl group, a2-ethylhexylcarbonyl group, a dodecylcarbonyl group, a phenylcarbonylgroup, a naphthylcarbonyl group, and a pyridylcarbonyl group); anacyloxy group (for example, an acetyloxy group, an ethylcarbonyloxygroup, a butylcarbonyloxy group, an octylcarbonyloxy group, adodecylcarbonyloxy group, and a phenylcarbonyloxy group); an amido group(for example, a methylcarbonylamino group, an ethylcarbonylamino group,a dimethylcarbonylamino group, a propylcarbonylamino group, apentylcarbonylamino group, a cyclohexylcarbonylamino group, a2-ethylhexylcarbonylamino group, an octylcarbonylamino group, adodecylcarbonylamino group, a phenylcarbonylamino group, and anaphthylcarbonylamino group); a carbamoyl group (for example, anaminocarbonyl group, a methylaminocarbonyl group, adimethylaminocarbonyl group, a propylaminocarbonyl group, apentylaminocarbonyl group, a cyclohexylaminocarbonyl group, anoctylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, adodecylaminocarbonyl group, a phenylaminocarbonyl group, anaphthylaminocarbonyl group, and a 2-pyridylaminocarbonyl group); aureido group (for example, a methylureido group, an ethylureido group, apentylureido group, a cyclohexylureido group, an octylureido group, adodecylureido group, a phenylureido group, a naphthylureido group, and a2-oyridylaminoureido group); a sulfinyl group (for example, amethylsulfinyl group, an ethylsulfinyl group, a butylsulfinyl group, acyclohexylsulfinyl group, a 2-ethylhexylsulfinyl group, adodecylsulfinyl group, a phenylsulfinyl group, a naphthylsulfinyl group,and a 2-pyridylsulfinyl group); an alkylsulfonyl group (for example, amethylsulfonyl group, an ethylsulfonyl group, a butylsulfinyl group, acyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group, and adodecylsulfonyl group, an arylsulfonyl group or a heteroarylsulfonylgroup (for example, a phenylsulfonyl group, a naphthylsulfonyl group,and a 2-pyridylsulfonyl group); an amino group (for example, an aminogroup, an ethylamino group, a dimethylamino group, a butylamino group, acyclopentylamino group, a dodecylamino group, an anilino group, anaphthylamino group, and a 2-pyridylamino group); a cyano group; a nitrogroup; a hydroxyl group; a mercapto group; a silyl group (for example, atrimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group,and a phenyldiethylsilyl group), and a phosphono group.

These substituents may further be substituted with the aforesaidsubstituents. Further, a plurality of these substituents may mutually bejoined to form a ring.

Of these, it is preferable that in Formula (A), at least one ofsubstituents represented by each of A1 and A2 in Formula (A) is anitrogen atom-containing substituent. Further, as the nitrogenatom-containing substituent, preferred are a carbazolyl group, acarbolynyl group, and a diarylamino group.

The aforesaid carbolynyl group is a group derived from the carbolinederivative represented by the aforesaid Formula (a), and in Formula (a),the substituent represented by Ra or Rb is as defined for thesubstituent represented by each of A1 and A2 in Formula (A).

Aryl of the diarylamino group is as defined for the substituentrepresented by each of A1 and A2 in Formula (A).

In N—R represented by X and Y of Formula (A), the substituentrepresented by R is as defined for the substituent represented by eachof A1 and A2. Examples of preferably employed ones include an alkylgroup, an alkenyl group, an alkynyl group, an aromatic hydrocarbongroup, an aromatic heterocyclic group, a heterocyclic group, analkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, acarbamoyl group, and a fluorinated hydrocarbon group. Specific examplesof the substituents are the same as those represented by each of aboveA1 and A2.

In Formula (A), divalent linking groups represented by each of L1, L2,and L3 include an alkylene group (for example, an ethylene group, atrimethylene group, a tetramethylene group, a propylene group, anethylethylene group, a pentamethylene group, and a hexamethylene group),an alkenylene group (for example, a vinylene group, a propenylene group,a butenylene group, a pentenylene group, a 1-methylvinylene group, a1-methylpropenylene group, a 2-methylpropenylene group, a1-methylpentenylene group, a 3-methylpentenylene group, a1-ethylvinylene group, a 1-ethylpropenylene group, a 1-ethylbutenylenegroup, and a 3-ethylbutenylene group), an alkynylene group (for example,an ethynylene group, a 1-propynylene group, a 1-butynylene group, a1-pentynylene group, a 1-hexnylene group, a 2-butynylene group, a2-pentynylene group, a 1-methylethynylene group, a3-methyl-1-propynylene group, and a 3-methyl-1-butynylene group), anarylene group (for example, an o-phenylene group, a m-phenylene group, ap-phenylene group, a naphthalenediyl group, an anthracenediyl group, anaphthacenediyl group, a pyrenediyl group, a naphthylnaphthalenediylgroup, a biphenyldiyl group (for example, a [1,1′-biphenyl]-4,4′-diylgroup and a 3,3′-biphenyldiyl group, and a 3,6-biphenyldiyl group),terphenyldiyl group, quaterphenyldiyl group, a quinquephenyldiyl group,a sexiphenyldiyl group, a septiphenyldiyl group, an octiphenyldiylgroup, a nobiphenyldiyl group, and a deciphenyldiyl group), aheteroarylene group (for example, a divalent group derived from thegroup consisting of a carbazole group, a carboline ring, adiazacarbazole ring (also referred to as a monoazacarboline group,indicating a ring structure formed in such a manner that one of thecarbon atoms constituting the carboline ring is replaced with a nitrogenatom), a triazole ring, a pyrrole ring, a pyridine ring, a pyrazinering, a quinoxaline ring, a thiophene ring, an oxadiazole ring, adibenzofuran ring, a dibenzothiophene ring and an indole ring), and adivalent heterocyclic group (for example, a divalent group derived froma pyrrolidine ring, a imidazolidine ring, a morpholine ring, and aoxazolidine ring), and a chalcogen atom such as oxygen and sulfur.

Further, employed may be a group which links via a hetero atom such asin an alkylimino group, a dialkylsilanediyl group, or a diarylgermandiylgroup.

Still further, as the aforesaid L3, preferred are an arylene group, aheteroarylene group, a divalent heterocyclic group, and an alkylenegroup. Of these, more preferred is the arylene group and most preferredis the m-phenylene group.

Specific examples of the phosphorescent compounds represented by Formula(A) of the present invention will now be listed, however the presentinvention is not limited thereto.

Synthesis of compounds represented by Formula (A) according to thepresent invention may be carried out based on the method known in theprior art or via referring to literatures (for example, conventionalliteratures which are described in the host compounds below).

An emission host compound of the present invention may be used withplural known host compounds. It is possible to control the transfer ofcharges by making use of a plurality of host compounds, which results inhigh efficiency of an organic EL element. In addition, it is possible tomix a different emission lights by making use of a plurality of emissiondopants that will be described later. Any required emission color can beobtained thereby.

Further, an emission host of the present invention may be either a lowmolecular weight compound or a polymer compound having a repeating unit,in addition to a low molecular weight compound provided with apolymerizing group such as a vinyl group and an epoxy group (anevaporation polymerizing emission host).

A known emission host which may be jointly used is preferably a compoundhaving a positive hole transporting ability and an electron transportingability, as well as preventing elongation of an emission wavelength andhaving a high Tg (a glass transition temperature).

As specific examples of an emission host compounds described in thefollowing Documents are preferable. For example, JP-A Nos. 2001-257076,2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786,2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056,2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568,2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453,2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861,2002-280183, 2002-299060, 2002-302516, 2002-305083, 2002-305084 and2002-308837.

(Emission Dopant)

The emission dopant of the present invention will now be described.

As light emitting dopants according to the present invention, employedmay be fluorescent dopants (also referred to as fluorescent compounds),phosphorescence emitting dopants (also referred to as phosphorescentdopants, phosphorescent compounds, phosphorescence emitting compounds,or phosphorescent dopants). However, in view of production of organic ELelements exhibiting higher light emission efficiency, as light emittingdopants (also referred simply to as light emitting materials) employedin the light emitting layer of the organic EL element and light emittingunits in the present invention, it is preferable to simultaneouslyincorporate the aforesaid host compounds and the phosphorescenceemitting dopants.

(Phosphorescence-Emitting Dopant)

A phosphorescence-emitting dopant of the present invention will bedescribed.

The phosphorescence-emitting dopant of the present invention is acompound, wherein emission from an excited triplet state thereof isobserved, specifically, emitting phosphorescence at room temperature(25° C.) and exhibiting a phosphorescence quantum yield of at least 0.01at 25° C. The phosphorescence quantum yield is preferably at least 0.1.

The phosphorescence quantum yield can be determined via a methoddescribed in page 398 of Bunko II of Dai 4 Han Jikken Kagaku Koza 7(Spectroscopy II of 4th Edition Lecture of Experimental Chemistry 7)(1992, published by Maruzen Co., Ltd.). The phosphorescence quantumyield in a solution can be determined using appropriate solvents.However, it is only necessary for the phosphorescence-emitting dopant ofthe present invention to exhibit the above phosphorescence quantum yieldusing any of the appropriate solvents.

Two kinds of principles regarding emission of a phosphorescence-emittingdopant are cited. One is an energy transfer-type, wherein carriersrecombine on a host compound on which the carriers are transferred toproduce an excited state of the host compound, and then via transfer ofthis energy to a phosphorescence-emitting dopant, emission from thephosphorescence-emitting dopant is realized. The other is a carriertrap-type, wherein a phosphorescence-emitting dopant serves as a carriertrap and then carriers recombine on the phosphorescence-emitting dopantto generate emission from the phosphorescence-emitting dopant. In eachcase, the excited state energy of the phosphorescence-emitting dopant isrequired to be lower than that of the host compound.

<<Compounds Represented by Formula (B)>>

Compounds represented by Formula (B) will now be described.

As phosphorescence emitting metal complexes according to the presentinvention, preferably employed are compounds represented by theaforesaid Formula (B).

In Formula (B), substituents represented by R₁ are as defined forsubstituents represented by each of A1 and A2 in Formula (A). Of thesesubstituents, preferred is an alkyl group or an aryl group, and morepreferred is an unsubstituted alkyl group or aryl group.

In formula (B), examples as a 5- to 7-membered ring formed by Z includea benzene ring, a naphthalene ring, a pyridine ring, a pyrimidine ring,a pyrrole ring, a thiophene ring, a pyrazole ring, an imidazole ring, anoxazole ring, and a thiazole ring. Of these, preferred is the benzenering.

In Formula (B), B₁-B₅ each represents a carbon atom, a nitrogen atom, anoxygen atom, or a sulfur atom, and at least one of them represents anitrogen atom. The ring formed by the aforesaid B1-B5 represents anaromatic heterocyclic ring having at least one nitrogen atom.

In Formula (B), examples of aromatic heterocyclic rings having at leastone nitrogen atom, which are formed via B₁-B₅, include a pyrrole ring, apyrazole ring, an imidazole ring, a triazole ring, a tetrazole ring, anoxazole ring, an isooxazole ring, a thiazole ring, an isothiazole ring,an oxadiazole ring, and a thiadiazole ring. Of these, preferred are thepyrazole ring and the imidazole ring, and particularly preferred is theimidazole ring.

These rings may be further substituted with the substituent representedby the aforesaid R₁. Preferred substituents include an unsubstitutedalkyl group and an unsubstituted aryl group.

Specific examples of bidentate ligands represented by X₁-L₁-X₂ inFormula (B) include phenylpyridine, phenylpyrazole, phenylimidazole,phenyltriazole, phenyltetrazole, pyrazabole, picolinic acid, andacetylacetone. Further, these ligands may further be substituted withthe substituent represented by the aforesaid R₁.

“m1” represents an integer of 1, 2, or 3, and m2 represents an integerof 0, 1, or 2, while m1+m2 is 2 or 3. In these cases, a case ispreferred in which m2 is 0.

As metals (including the case of metal ions) represented by M₁ inFormula (B), employed are transition metal elements (also referredsimply to as transition metals) of Groups 8-10 in the element periodictable. Of these, preferred are iridium and platinum, while iridium ismore preferred.

Incidentally, phosphorescence emitting metal complexes, represented byFormula (B), may or may not incorporate polymerizable groups or reactivegroups.

Specific examples of phosphorescence emitting metal complexes,represented by formula (B), are listed below, however the presentinvention is not limited thereto.

The phosphorescence emitting metal complex represented by Formula (B) ofthe present invention can be synthesized by referring to a methoddescribed, for example, in Inorg. Chem., Vol. 40, pages 1704-1711.

Further, in the present invention, phosphorescence emitting dopants areappropriately selected from conventional ones employed in the lightemitting layer of the organic EL element and simultaneously employed

Of conventional ones, as phosphorescence emitting dopants, preferred arecomplex based compounds incorporating metals in Groups 8-10 in theelement periodic table. Of these, more preferred are iridium compounds,osmium compounds, or platinum compounds (being platinum complex basedcompounds), and rare earth metal complexes, and of these, most preferredare iridium compounds.

Specific examples of compounds which are employed as conventionalphosphorescence emitting dopants, which may simultaneously be employed,are listed below, however the present invention is not limited thereto.

(Fluorescent Dopants (also referred to as Fluorescent Compounds))

As fluorescent dopants, listed are coumarin based dyes, pyran baseddyes, cyanine based dyes, croconium based dyes, squarylium based dyes,oxobenzanthracene based dyes, fluorescein based dyes, Rhodamine baseddyes, pyrylium based dyes, perylene based dyes, stilbene based dyes,polythiophene based dyes, or rare earth complex based fluorescentmaterials.

An injection layer, an inhibition layer, and an electron transportlayer, which are employed as a constituting layer of the organic ELelement of the present invention will now be described.

<Injection Layer: Electron Injection Layer, Positive Hole InjectionLayer>

An injection layer is appropriately provided and includes an electroninjection layer and a positive hole injection layer, which may bearranged between an anode and an emitting layer or a positive transferlayer, and between a cathode and an emitting layer or an electrontransport layer, as described above.

An injection layer is a layer which is arranged between an electrode andan organic layer to decrease an operating voltage and to improve anemission luminance, which is detailed in volume 2, chapter 2 (pp.123-166) of “Organic EL Elements and Industrialization Front thereof(Nov. 30, 1998, published by N. T. S Corp.)”, and includes a positivehole injection layer (an anode buffer layer) and an electron injectionlayer (a cathode buffer layer).

An anode buffer layer (a positive hole injection layer) is also detailedin such as JP-A 9-45479, 9-260062 and 8-288069, and specific examplesinclude such as a phthalocyanine buffer layer comprising such as copperphthalocyanine, an oxide buffer layer comprising such as vanadium oxide,an amorphous carbon buffer layer, and a polymer buffer layer employingconductive polymer such as polythiophene.

A cathode buffer layer (an electron injection layer) is also detailed insuch as JP-A 6-325871, 9-17574 and 10-74586, and specific examplesinclude a metal buffer layer comprising such as strontium and aluminum,an alkali metal compound buffer layer comprising such as lithiumfluoride, an alkali earth metal compound buffer layer comprising such asmagnesium fluoride, and an oxide buffer layer comprising such asaluminum oxide. The above-described buffer layer (injection layer) ispreferably a very thin layer, and the layer thickness is preferably in arange of 0.1-5 μm although it depends on a raw material.

<Inhibition Layer: Positive Hole Inhibition Layer, Electron InhibitionLayer>

An inhibition layer is appropriately provided in addition to the basicconstitution layers composed of organic thin layers as described above.Examples are described in such as JP-A Nos. 11-204258 and 11-204359 andp. 237 of “Organic EL Elements and Industrialization Front Thereof (Nov.30 (1998), published by N. T. S Corp.)” is applicable to a positive holeinhibition (hole block) layer according to the present invention.

A positive hole inhibition layer, in a broad meaning, is provided with afunction of electron transport layer, being comprised of a materialhaving a function of transporting an electron but a very small abilityof transporting a positive hole, and can improve the recombinationprobability of an electron and a positive hole by inhibiting a positivehole while transporting an electron.

Further, a constitution of an electron transport layer described latercan be appropriately utilized as a positive hole inhibition layeraccording to the present invention.

The positive hole inhibition layer of the organic EL element of thepresent invention is preferably arranged adjacent to the light emittinglayer.

It is preferable that the positive hole inhibition layer incorporatescarbazole derivatives listed as a host compound described above.

Further, in the present intention, in the case in which a plurality oflight emitting layers which differ in a plurality of different emittedlight colors, it is preferable that the light emitting layer whichresults in the shortest wavelength of the emitted light maximumwavelength is nearest to the anode in all light emitting layers.However, in such a case, it is preferable to additionally arrange thepositive hole inhibition layer between the aforesaid shortest wavelengthlayer and the light emitting layer secondly near the anode. Further, atleast 50% by weight of the compounds incorporated in the positive holeinhibition layer arranged in the aforesaid position preferably exhibitsthe ionization potential which is greater by at least 0.3 eV than thatof the host compounds of the aforesaid shortest wavelength lightemitting layer.

The ionization potential is defined as energy which is necessary torelease electrons in the HOMO (being the highest occupied molecularorbital) to the vacuum level, and may be determined via, for example,the method described below.

-   (1) By employing Gaussian98 (Gauaaian98, Revision A. 11. 4, M. J.    Frisch, et al. Gaussian 98(Gaussian98, Revision A. 11. 4, M. J.    Frisch, et al, Gaussian, Inc., Pittsburg h PA, 2002), which is a    molecular orbital calculation software, produced by Gaussian Co. in    the United State of America, and by employing B3LYP/6-31G* as a key    word, the value (in terms of corresponding eV unit) was computed,    and it is possible to obtain the ionization potential by rouging off    the second decimal point. The background, in which the resulting    calculated values are effective, is that the calculated values    obtained by the above method exhibit high relationship with the    experimental values.-   (2) It is possible to determine the ionization potential via a    method in which ionization potential is directly determined    employing a photoelectron spectrometry. For example, by employing a    low energy electron spectrophotometer “Model AC-1”, produced by    Riken Keiki Co., or appropriately employ a method known as an    ultraviolet light electron spectrometry.

On the other hand, the electron inhibition layer, as described herein,has a function of the positive hole transport layer in a broad sense,and is composed of materials having markedly small capability ofelectron transport, while having capability of transporting positiveholes and enables to enhance the recombination probability of electronsand positive holes by inhibiting electrons, while transportingelectrons. Further, it is possible to employ the constitution of thepositive hole transport layer, described below, as an electroninhibition layer when needed. The thickness of the positive holeinhibition layer and the electron transport layer according to thepresent invention is preferably 3-100 nm, but is more preferably 5-30nm.

<Positive Hole Transport Layer>

A positive hole transport layer contains a material having a function oftransporting a positive hole, and in a broad meaning, a positive holeinjection layer and an electron inhibition layer are also included in apositive hole transport layer. A single layer of or plural layers of apositive hole transport layer may be provided.

A positive hole transport material is those having any one of a propertyto inject or transport a positive hole or a barrier property to anelectron, and may be either an organic substance or an inorganicsubstance. For example, listed are a triazole derivative, an oxadiazolederivative, an imidazole derivative, a polyarylalkane derivative, apyrazolone derivative, a phenylenediamine derivative, an arylaminederivative, an amino substituted chalcone derivative, an oxazolederivatives, a styrylanthracene derivative, a fluorenone derivative, ahydrazone derivative, a stilbene derivative, a silazane derivative, ananiline type copolymer, or conductive polymer oligomer and specificallypreferably such as thiophene oligomer.

As a positive hole transport material, those described above can beutilized, however, it is preferable to utilized a porphyrin compound, anaromatic tertiary amine compound and a styrylamine compound, andspecifically preferably an aromatic tertiary amine compound.

Typical examples of an aromatic tertiary amine compound and astyrylamine compound include N,N,N′,N′-tetraphenyl-4,4′-diaminophenyl;N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine(TDP); 2,2-bis(4-di-p-tolylaminophenyl)propane;1,1-bis(4-di-p-tolylaminophenyl)cyclohexane; N,N,N′,N′-tetra-p-tolyl 4,4′-diaminobiphenyl;1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;bis(4-dimethylamino-2-methyl)phenylmethane;bis(4-di-p-tolylaminophenyl)phenylmethane; N,N′-diphenyl-N,N′-di(4-methoxyphenyl)-4,4′-diaminobiphenyl;N,N,N′,N′-tetraphenyl-4,4′-diaminophenylether;4,4′-bis(diphenylamino)quadriphenyl; N,N,N-tri(p-tolyl)amine;4-(di-p-tolylamino)-4′-[4-(di-p-triamino)styryl]stilbene; 4-N,N-diphenylamino-(2-diphenylvinyl)benzene;3-methoxy-4′-N,N-diphenylaminostilbene; and N-phenylcarbazole, inaddition to those having two condensed aromatic rings in a moleculedescribed in U.S. Pat. No. 5,061,569, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NDP), and 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MDTDATA), inwhich three of triphenylamine units are bonded in a star burst form,described in JP-A 4-308688.

Polymer materials, in which these materials are introduced in a polymerchain or constitute the main chain of polymer, can be also utilized.Further, an inorganic compound such as a p type-Si and a p type-SiC canbe utilized as a positive hole injection material and a positive holetransport material

Further, it is possible to employ so-called p type positive holetransport materials, as described in Japanese Patent Publication Open toPublic Inspection (hereinafter referred to as JP-A) No. 11-251067, andJ. Huang et al. reference (Applied Physics Letters 80 (2002), p. 139).In the present invention, since high efficiency light emitting elementsare prepared, it is preferable to employ these materials.

This positive hole transport layer can be prepared by forming a thinlayer made of the above-described positive hole transport materialaccording to a method well known in the art such as a vacuum evaporationmethod, a spin coating method, a cast method, an inkjet method and a LBmethod.

The layer thickness of a positive hole transport layer is notspecifically limited, however, it is generally 5 nm-5 μm, and preferably5 nm-200 nm. This positive transport layer may have a single layerstructure comprised of one or not less than two types of the abovedescribed materials.

Further, it is possible to employ a positive hole transport layer of ahigher p property which is doped with impurities. As its example, listedare those described in each of JP-A Nos. 4-297076, 2000-196140,2001-102175, as well as in J. Appl. Phys., 95, 5773 (2004).

In the present invention, it is preferable to employ a positive holetransport layer of such a high p property, since it is possible toproduce an element of lower electric power consumption.

<Electron Transport Layer>

An electron transport layer is comprised of a material having a functionto transfer an electron, and an electron injection layer and a positivehole inhibition layer are included in an electron transport layer in abroad meaning. A single layer or plural layers of an electron transportlayer may be provided.

Heretofore, when an electron transport layer is composed of single layerand a plurality of layers, electron transport materials (alsofunctioning as a positive hole inhibition material) employed in theelectron transport layer adjacent to the cathode side with respect tothe light emitting layer, electrons ejected from the cathode may betransported to the light emitting layer. As such materials, any of theconventional compounds may be selected and employed.

Examples of these compounds include such as a nitro-substituted fluorenederivative, a diphenylquinone derivative, a thiopyradineoxidederivative, carbodiimide, a fluorenylidenemethane derivative,anthraquinonedimethane, an anthraquinone derivative, an anthronederivative and an oxadiazole derivative.

Further, a thiazole derivative in which an oxygen atom in the oxadiazolering of the above-described oxadiazole derivative is substituted by asulfur atom, and a quinoxaline derivative having a quinoxaline ringwhich is known as an electron attracting group can be utilized as anelectron transport material.

Polymer materials, in which these materials are introduced in a polymerchain or these materials form the main chain of polymer, can be alsoutilized.

Further, a metal complex of a 8-quinolinol derivative such astris(8-quinolinol)aluminum (Alq), tris(5,7-dichloro-8-quinolinol)aluminum, tris(5,7-dibromo-8-quinolinol)aluminum,tris(2-methyl-8-quinolinol)aluminum, tris(5-methyl-8-quinolinol)aluminumand bis(8-quinolinol)zinc (Znq); and metal complexes in which a centralmetal of the aforesaid metal complexes is substituted by In, Mg, Cu, Ca,Sn, Ga or Pb, can be also utilized as an electron transport material.

Further, metal-free or metal phthalocyanine, or those the terminal ofwhich is substituted by an alkyl group and a sulfonic acid group, can bepreferably utilized as an electron transport material. Further,distyrylpyrazine derivative, which has been exemplified as a material ofan emitting layer, can be also utilized as an electron transportmaterial, and, similarly to the case of a positive hole injection layerand a positive hole transfer layer, an inorganic semiconductor such asan n-type-Si and an n-type-SiC can be also utilized as an electrontransport material.

This electron transport layer can be prepared by forming a thin layermade of the above-described electron transport material according to amethod well known in the art such as a vacuum evaporation method, a spincoating method, a cast method, an inkjet method and a LB method.

The layer thickness of an electron transport layer is not specificallylimited; however, it is generally 5 nm-5 μm, and preferably 5 nm-200 nm.This electron transport layer may have a single layer structurecomprised of one or not less than two types of the above describedmaterials.

Further, it is possible to employ an electron transport layer doped withimpurities, which exhibits high n property. Examples thereof includethose, described in JP-A Nos. 4-297076, 10-270172, 2000-196140,2001-102175, as well as J. Appl. Phys., 95, 5773 (2004).

The present invention is preferable since by employing an electrontransport layer of such a high n property electron transport layer, itis possible to preparer an element of further lowered electric powerconsumption.<Anode>

As an anode according to an organic EL element of the present invention,those comprising metal, alloy, a conductive compound, which is providedwith a large work function (not less than 4 eV), and a mixture thereofas an electrode substance are preferably utilized. Specific examples ofsuch an electrode substance include a conductive transparent materialsuch as metal like Au, CuI, indium tin oxide (ITO), SnO₂ and ZnO.Further, a material such as IDIXO (In₂O₃—ZnO), which can prepare anamorphous and transparent electrode, may be also utilized.

As for an anode, these electrode substances may be made into a thinlayer by a method such as evaporation or spattering and a pattern of adesired form may be formed by means of photolithography, or in the caseof requirement of pattern precision is not so severe (not less than 100μm), a pattern may be formed through a mask of a desired form at thetime of evaporation or spattering of the above-described substance.

Alternatively, when coatable materials such as organic electricallyconductive compounds are employed, it is possible to employ a wet systemfilming method such as a printing system or a coating system.

When emission is taken out of this anode, the transmittance ispreferably set to not less than 10% and the sheet resistance as an anodeis preferably not more than a few hundreds Ω/□. Further, although thelayer thickness depends on a material, it is generally selected in arange of 10-1,000 nm and preferably of 10-200 nm.

<Cathode>

On the other hand, as a cathode according to the present invention,metal, alloy, a conductive compound and a mixture thereof, which have asmall work function (not more than 4 eV), are utilized as an electrodesubstance. Specific examples of such an electrode substance includessuch as sodium, sodium-potassium alloy, magnesium, lithium, amagnesium/copper mixture, a magnesium/silver mixture, amagnesium/aluminum mixture, a magnesium/indium mixture, analuminum/aluminum oxide (Al₂O₃) mixture, indium, a lithium/aluminummixture and rare earth metal.

Among them, with respect to an electron injection property anddurability against such as oxidation, preferable are a mixture ofelectron injecting metal with the second metal which is stable metalhaving a work function larger than electron injecting metal, such as amagnesium/silver mixture, a magnesium/aluminum mixture, amagnesium/indium mixture, an aluminum/aluminum oxide (Al₂O₃) mixture anda lithium/aluminum mixture, and aluminum. As for a cathode, theseelectrode substances may be made into a thin layer by a method such asevaporation or spattering.

Further, the sheet resistance as a cathode is preferably not more than afew hundreds Ω/□ and the layer thickness is generally selected in arange of 10 nm-5 μm and preferably of 50-200 nm.

Herein, to transmit emission, either one of an anode or a cathode of anorganic EL element is preferably transparent or translucent to improvethe mission luminance.

Further, after forming, on the cathode, the above metals at a filmthickness of 1-20 nm, it is possible to prepare a transparent ortranslucent cathode in such a manner that electrically conductivetransparent materials are prepared thereon. By applying the above, it ispossible to produce an element in which both anode and cathode aretransparent.

<Substrate>

A substrate according to an organic EL element of the present inventionis not specifically limited with respect to types of such as glass andplastics. They me be transparent or opaque.

However, a transparent substrate is preferable when the emitting lightis taken from the side of substrate. Substrates preferably utilizedincludes such as glass, quartz and transparent resin film. Aspecifically preferable substrate is resin film capable of providing anorganic EL element with a flexible property.

Resin film includes such as: polyesters such as polyethyleneterephthalate (PET) and polyethylene naphthalate (PEN); polyethylene,polypropyrene; cellulose esters or their derivatives such as cellophane,cellulose diacetate, cellulose triacetate, cellulose acetate butylate,cellulose acetate propionate (CAP), cellulose acetate phthalate (TAC)and cellulose nitrate; polyvinylidene chloride, polyvinyl alcohol,polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate,norbornene resin, polymethylpentene, polyether ketone, polyimide,polyether sulfone (PES), polyphenylene sulfide, polysulfones,polyetherimide, polyether ketone imide, polyamide, fluororesin, Nylon,polymethylmethacrylate, acrylic resin, polyacrylate; and cycloolefineresins such as ARTON (produced by JSR Co. Ltd.) and APEL (produce byMitsui Chemicals, Inc.)

On the surface of a resin film, formed may be a film incorporatinginorganic and organic compounds or a hybrid film of both. Barrier filmsare preferred at a water vapor permeability (25±0.5° C., and relativehumidity (90±2) % RH) of at most 0.01 g/(m²·24 h), determined based onJIS K 7129-1992. Further, high barrier films are preferred at an oxygenpermeability of at most 1×10⁻³ ml/(m²·24 h·MPa), and at a water vaporpermeability of at most 10⁻⁵ g/(m²·24 h), determined based on JIS K7126-1987.

As materials forming a barrier film, employed may be those which retardpenetration of moisture and oxygen, which deteriorate the element. Forexample, it is possible to employ silicon oxide, silicon dioxide, andsilicon nitride. Further, in order to improve the brittleness of theaforesaid film, it is more preferable to achieve a laminated layerstructure of inorganic layers and organic layers. The laminating orderof the inorganic layer and the organic layer is not particularlylimited, but it is preferable that both are alternatively laminated aplurality of times.

Barrier film forming methods are not particularly limited, and examplesof employable methods include a vacuum deposition method, a sputteringmethod, a reactive sputtering method, a molecular beam epitaxy method, acluster ion beam method, an ion plating method, a plasma polymerizationmethod, a plasma CVD method, a laser CVD method, a thermal CVD method,and a coating method. Of these, specifically preferred is a methodemploying an atmospheric pressure plasma polymerization method,described in JP-A No. 2004-68143.

Examples of opaque support substrates include metal plates such aluminumor stainless steel, films, opaque resin substrates, and ceramicsubstrates.

The external extraction efficiency of light emitted by the organic ELelement of the present invention is preferably at least 1% at roomtemperature, but is more preferably at least 5%.

External extraction quantum yield (%)=the number of photons emitted bythe organic EL element to the exterior/the number of electrons fed toorganic EL element

Further, even by simultaneously employing color hue improving filterssuch as a color filter, simultaneously employed may be color conversionfilters which convert emitted light color from the organic EL element tomulticolor by employing fluorescent materials. When the color conversionfilters are employed, it is preferable that λmax of light emitted by theorganic EL element is at least 480 nm.

<<Sealing>>

As sealing means employed in the present invention, listed may be, forexample, a method in which sealing members, electrodes, and a supportingsubstrate are subjected to adhesion via adhesives.

The sealing members may be arranged to cover the display region of anorganic EL element, and may be an engraved plate or a flat plate.Neither transparency nor electrical insulation is limited.

Specifically listed are glass plates, polymer plate-films, metal plates,and films. Specifically, it is possible to list, as glass plates,soda-lime glass, barium-strontium containing glass, lead glass,aluminosilicate glass, borosilicate glass, bariumborosilicate glass, andquartz.

Further, listed as polymer plates may be polycarbonate, acryl,polyethylene terephthalate, polyether sulfide, and polysulfone. As ametal plate, listed are those composed of at least one metal selectedfrom the group consisting of stainless steel, iron, copper, aluminummagnesium, nickel, zinc, chromium, titanium, molybdenum, silicon,germanium, and tantalum, or alloys thereof.

In the present invention, since it is possible to convert the element toa thin film, it is possible to preferably employ a metal film. Further,the oxygen permeability of the polymer film is preferably at most 1×10⁻³ml/(m²·24 h·MPa), determined by the method based on JIS K 7126-1987,while its water vapor permeability (at 25±0.5° C. and relative humidity(90±2) %) is at most 10⁻⁵ g/(m²·24 h), determined by the method based onJIS K 7129-1992.

Conversion of the sealing member into concave is carried out employing asand blast process or a chemical etching process. In practice, asadhesives, listed may be photo-curing and heat-curing types having areactive vinyl group of acrylic acid based oligomers and methacrylicacid, as well as moisture curing types such as 2-cyanoacrylates.

Further listed may be thermal and chemical curing types (mixtures of twoliquids) such as epoxy based ones. Still further listed may be hot-melttype polyamides, polyesters, and polyolefins. Yet further listed may becationically curable type ultraviolet radiation curable type epoxy resinadhesives.

In addition, since an organic EL element is occasionally deterioratedvia a thermal process, those are preferred which enable adhesion andcuring between room temperature and 80° C. Further, desiccating agentsmay be dispersed into the aforesaid adhesives. Adhesives may be appliedonto sealing portions via a commercial dispenser or printed on the samein the same manner as screen printing.

Further, it is appropriate that on the outside of the aforesaidelectrode which interposes the organic layer and faces the supportsubstrate, the aforesaid electrode and organic layer are covered, and inthe form of contact with the support substrate, inorganic and organicmaterial layers are formed as a sealing film. In this case, as materialsforming the aforesaid film may be those which exhibit functions toretard penetration of those such as moisture or oxygen which results indeterioration. For example, it is possible to employ silicon oxide,silicon dioxide, and silicon nitride.

Still further, in order to improve brittleness of the aforesaid film, itis preferable that a laminated layer structure is formed, which iscomposed of these inorganic layers and layers composed of organicmaterials. Methods to form these films are not particularly limited. Itis possible to employ, for example, a vacuum deposition method, asputtering method, a reactive sputtering method, a molecular beamepitaxy method, a cluster ion beam method, an ion plating method, aplasma polymerization method, an atmospheric pressure plasmapolymerization method, a plasma CVD method, a thermal CVD method, and acoating method.

In a gas phase and a liquid phase, it is preferable to inject inertgases such as nitrogen or argon, and inactive liquids such asfluorinated hydrocarbon or silicone oil into the space between thesealing member and the surface region of the organic EL element.Further, it is possible to form vacuum. Still further, it is possible toenclose hygroscopic compounds in the interior.

Examples of hygroscopic compounds include metal oxides (for example,sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesiumoxide, and aluminum oxide); sulfates (for example, sodium sulfate,calcium sulfate, magnesium sulfate, and cobalt sulfate); metal halides(for example, calcium chloride, magnesium chloride, cesium fluoride,tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, andmagnesium iodide); perchlorates (for example, barium perchlorate andmagnesium perchlorate). In sulfates, metal halides, and perchlorates,suitably employed are anhydrides.

<<Protective Film and Protective Plate>>

The aforesaid sealing film on the side which nips the organic layer andfaces the support substrate or on the outside of the aforesaid sealingfilm, a protective or a protective plate may be arranged to enhance themechanical strength of the element. Specifically, when sealing isachieved via the aforesaid sealing film, the resulting mechanicalstrength is not always high enough, whereby it is preferable to arrangethe protective film or the protective plate described above. Usablematerials for these include glass plates, polymer plate-films, and metalplate-films which are similar to those employed for the aforesaidsealing. However, in terms of light weight and a decrease in thickness,it is preferable to employ polymer films.

<<Light Extraction>>

It is generally known that an organic EL element emits light in theinterior of the layer exhibiting the refractive index (being about1.7-about 2.1) which is greater than that of air, whereby only about15-about 20% of light generated in the light emitting layer isextracted.

This is due to the fact that light incident to an interface (being aninterface of a transparent substrate to air) at an angle of θ which isat least critical angle is not extracted to the exterior of the elementdue to the resulting total reflection, or light is totally reflectedbetween the transparent electrode or the light emitting layer and thetransparent substrate, and light is guided via the transparent electrodeor the light emitting layer, whereby light escapes in the direction ofthe element side surface.

Means to enhance the efficiency of the aforesaid light extractioninclude, for example, a method in which roughness is formed on thesurface of a transparent substrate, whereby total reflection isminimized at the interface of the transparent substrate to air (U.S.Pat. No. 4,774,435), a method in which efficiency is enhanced in such amanner that a substrate results in light collection (JP-A No.63-314795), a method in which a reflection surface is formed on the sideof the element (JP-A No. 1-220394), a method in which a flat layer of amiddle refractive index is introduced between the substrate and thelight emitting body and an antireflection film is formed (JP-A No.62-172691), a method in which a flat layer of a refractive index whichis equal to or less than the substrate is introduced between thesubstrate and the light emitting body (JP-A No. 2001-202827), and amethod in which a diffraction grating is formed between the substrateand any of the layers such as the transparent electrode layer or thelight emitting layer (including between the substrate and the outside)(JP-A No. 11-283751).

In the present invention, it is possible to employ these methods whilecombined with the organic EL element of the present invention. Of these,it is possible to appropriately employ the method in which a flat layerof a refractive index which is equal to or less than the substrate isintroduced between the substrate and the light emitting body and themethod in which a diffraction grating is formed between the substrateand any of the layers such as the transparent electrode layer or thelight emitting layer (including between the substrate and the outside).

By combining these means, the present invention enables the productionof elements which exhibit higher luminance or excel in durability.

When a low refractive index medium of a thickness, which is greater thanthe wavelength of light, is formed between the transparent electrode andthe transparent substrate, the extraction efficiency of light emittedfrom the transparent electrode to the exterior increases as therefractive index of the medium decreases.

As materials of the low refractive index layer, listed are, for example,aerogel, porous silica, magnesium fluoride, and fluorine based polymers.Since the refractive index of the transparent substrate is commonlyabout 1.5-about 1.7, the refractive index of the low refractive indexlayer is preferably at most approximately 1.5, but is more preferably atmost 1.35.

Further, thickness of the low refractive index medium is preferably atleast two times the wavelength in the medium. The reason is that whenthe thickness of the low refractive index medium reaches nearly thewavelength of light so that electromagnetic waves oozed via evernescententer into the substrate, effects of the low refractive index layer arelowered.

The method in which the interface which results in total reflection or adiffraction grating is introduced in any of the media is characterizedin that light extraction efficiency is significantly enhanced.

The above method works as follows. By utilizing properties of thediffraction grating capable of changing the light direction to thespecific direction different from diffraction via so-called Braggdiffraction such as primary diffraction or secondary diffraction of thediffraction grating, of light emitted from the light emitting layer,light, which is not emitted to the exterior due to total reflectionbetween layers, is diffracted via introduction of a diffraction gratingbetween any layers or in a medium (in the transparent substrate and thetransparent electrode) so that light is extracted to the exterior.

It is preferable that the introduced diffraction grating exhibits atwo-dimensional periodic refractive index. The reason is as follows.Since light emitted in the light emitting layer is randomly generated toall directions, in a common one-dimensional diffraction gratingexhibiting a periodic refractive index distribution only in a certaindirection, light which travels to the specific direction is onlydiffracted, whereby light extraction efficiency is not sufficientlyenhanced.

However, by changing the refractive index distribution to atwo-dimensional one, light, which travels to all directions, isdiffracted, whereby the light extraction efficiency is enhanced.

As noted above, a position to introduce a diffraction grating may bebetween any layers or in a medium (in a transparent substrate or atransparent electrode). However, a position near the organic lightemitting layer, where light is generated, is desirous.

In this case, the cycle of the diffraction grating is preferably about½-about 3 times the wavelength of light in the medium.

The preferable arrangement of the diffraction grating is such that thearrangement is two-dimensionally repeated in the form of a squarelattice, a triangular lattice, or a honeycomb lattice.

<<Light Collection Sheet>>

Via a process to arrange a structure such as a micro-lens array shape onthe light extraction side of the organic EL element of the presentinvention or via combination with a so-called light collection sheet,light is collected in the specific direction such as the front directionwith respect to the light emitting element surface, whereby it ispossible to enhance luminance in the specific direction.

In an example of the micro-lens array, square pyramids to realize a sidelength of 30 μm and an apex angle of 90 degrees are two-dimensionallyarranged on the light extraction side of the substrate. The side lengthis preferably 10-100 μm. When it is less than the lower limit,coloration results due to generation of diffraction effects, while whenit exceeds the upper limit, the thickness increases undesirably.

It is possible to employ, as a light collection sheet, for example, onewhich is put into practical use in the LED backlight of liquid crystaldisplay devices. It is possible to employ, as such a sheet, for example,the luminance enhancing film (BEF), produced by Sumitomo 3M Limited. Asshapes of a prism sheet employed may be, for example, Δ shaped stripesof an apex angle of 90 degrees and a pitch of 50 μm formed on a basematerial, a shape in which the apex angle is rounded, a shape in whichthe pitch is randomly changed, and other shapes.

Further, in order to control the light radiation angle from the lightemitting element, simultaneously employed may be a light diffusionplate-film. For example, it is possible to employ the diffusion film(LIGHT-UP), produced by Kimoto Co., Ltd.

<<Preparation Method of Organic EL Element>>

As one example of the preparation method of the organic EL element ofthe present invention, the preparation method of the organic EL elementcomposed of anode/positive hole injection layer/positive hole transportlayer/light emitting layer/electron transport layer/electron injectionlayer/cathode will be described.

Initially, a thin film composed of desired electrode substances, forexample, anode substances is formed on an appropriate base material toreach a thickness of at most 1 μm but preferably 10-200 nm, employing amethod such as vapor deposition or sputtering, whereby an anode isprepared.

Subsequently, on the above, formed are organic compound thin layersincluding a positive hole injection layer, a positive hole transportlayer, a light emitting layer, a positive hole inhibition layer, anelectron transport layer, and an electron injection layer, which areorganic EL element materials.

Methods to form each of these layers include, as described above, avapor deposition method and a wet process (a spin coating method, acasting method, an ink-jet method, and a printing method). In thepresent invention, in view of easy formation of a homogeneous film andrare formation of pin holes, preferred is film formation via the coatingmethod such as the spin coating method, the ink-jet method, or theprinting method, and of these, the ink-jet method is particularlypreferred.

In the present invention, during formation of the light emitting layer,it is preferable that the layer is formed via a coating method employinga liquid which is prepared by dissolving or dispersing organic metalcomplexes according to the present invention. It is specificallypreferable that the coating method is the ink-jet method.

As liquid media which are employed to dissolve or disperse organic metalcomplexes according to the present invention, employed may be, forexample, ketones such as methyl ethyl ketone or cyclohexanone, fattyacid esters such as ethyl acetate, halogenated hydrocarbons such asdichlorobenzene, and organic solvents such as DMF or DMSO.

Further, with regard to dispersion methods, it is possible to achievedispersion employing dispersion methods such as ultrasonic waves, highshearing force dispersion or media dispersion.

After forming these layers, a thin layer composed of cathode materialsis formed on the above layers via a method such as vapor deposition orsputtering so that the film thickness reaches at most 1 μm, but ispreferably in the range of 50-200 nm, whereby a cathode is arranged, andthe desired organic EL element is prepared.

Further, by reversing the preparation order, it is possible to achievepreparation in order of a cathode, an electron injection layer, anelectron transport layer, a light emitting layer, a positive holetransport layer, a positive hole injection layer, and an anode. Whendirect current voltage is applied to the multicolor display deviceprepared as above, the anode is employed as + polarity, while thecathode is employed as − polarity. When 2-40 V is applied, it ispossible to observe light emission. Further, alternating current voltagemay be applied. The wave form of applied alternating current voltage isnot specified.

<<Application>>

It is possible to employ the organic EL element of the present inventionas display devices, displays, and various types of light emittingsources. Examples of light emitting sources include, but are not limitedto lighting apparatuses (home lighting and car lighting), clocks,backlights for liquid crystals, sign advertisements, signals, lightsources of light memory media, light sources of electrophotographiccopiers, light sources of light communication processors, and lightsources of light sensors.

It is effectively employed especially as backlights of liquid crystaldisplay devices and lighting sources.

If needed, the organic EL element of the present invention may undergopatterning via a metal mask or an ink-jet printing method during filmformation. When the patterning is carried out, only an electrode mayundergo patterning, an electrode and a light emitting layer may undergopatterning, or all element layers may undergo patterning. Duringpreparation of the element, it is possible to employ conventionalmethods.

Color of light emitted by the organic EL element of the presentinvention and compounds according to the present invention is specifiedas follows. In FIG. 4.16 on page 108 of “Shinpen Shikisai KagakuHandbook (New Edition Color Science Handbook)” (edited by The ColorScience Association of Japan, Tokyo Daigaku Shuppan Kai, 1985), valuesdetermined via a spectroradiometric luminance meter CS-1000 (produced byKonica Minolta Sensing Inc.) are applied to the CIE chromaticitycoordinate, whereby the color is specified.

Further, when the organic EL element of the present invention is a whiteelement, “white”, as described herein, means that when 2-degree viewingangle front luminance is determined via the aforesaid method,chromaticity in the CIE 1931 Color Specification System is within theregion of X=0.33±0.07 and Y=0.33±0.07.

EXAMPLES

The present invention will now be described with reference to examples,however the present invention is not limited thereto.

Example 1

<<Preparation of Organic EL Element 1-1>>

Patterning was applied to a substrate (NA45 produced by NH Techno GlassCorp.) on which a 100 nm film of ITO (indium tin oxide) was formed, as aanode, on the above 100 mm×100 mm×1.1 mm glass substrate. Thereafter,the above transparent support substrate provided with the ITOtransparent electrode underwent ultrasonic washing with isopropylalcohol, dried via desiccated nitrogen gas, and underwent UV ozonewashing for 5 minutes.

The resulting transparent support substrate was fixed via the substrateholder of a commercial vacuum deposition apparatus. Separately, 200 mgof α-NPD was placed in a molybdenum resistance heating boat, 200 mg ofCBP as a host compound was placed in another molybdenum resistanceheating boat, 200 mg of BCP was placed in further another molybdenumresistance heating boat, 100 mg of Exemplified Compound I-1 was placedin yet another molybdenum resistance heating boat, and 200 mg of Alq₃was placed in still yet another molybdenum resistance heating boat, andthe resulting boats were fitted in the vacuum deposition apparatus.

Subsequently, after reducing the pressure of the vacuum tank to 4×10⁻⁴Pa, the aforesaid heating boat, in which α-NPD was placed, was heatedvia application of electric current and deposition was carried out ontothe transparent support substrate at a deposition rate of 0.1 nm/second,whereby a 40 nm thick positive hole transport layer was arranged.

Further, the aforesaid heating boats in which CBP and ExemplifiedCompound 1-1 were placed respectively, were heated via application ofelectric current and co-deposition was carried out onto the aforesaidpositive hole transport layer at a deposition rate of 0.2 nm/second and0.012 nm/second, respectively, whereby a 40 nm thick light emittinglayer was arranged. The substrate during deposition had a roomtemperature.

Further, the aforesaid heating boat, in which BCP was placed, was heatedvia application of electric current and deposition was carried out ontothe aforesaid light emitting layer at a deposition rate of 0.1nm/second, whereby a 10 nm thick positive hole inhibition layer wasarranged.

Further, the aforesaid heating boat, in which Alq_(a) was placed, washeated via application of electric current and deposition was carriedout onto the aforesaid positive hole inhibition layer at a depositionrate of 0.1 nm/second, whereby a 40 nm thick electron transport layerwas arranged. The substrate during deposition had a room temperature.

Subsequently, 0.5 nm lithium fluoride and 110 nm aluminum were depositedto form a cathode, whereby Organic EL Element 1-1 was prepared.

<<Preparation of Organic EL Elements 1-2 through 1-15>>

Organic EL Elements 1-2 through 1-15 were prepared in the same manner asOrganic EL Element 1-1, except that CBP which was the host compound inthe light emitting layer was replaced with each of the compounds listedin Table 1, and Exemplified Compound I-1 was replaced with each of thecompounds listed in Table 1.

<<Evaluation of Organic EL Elements 1-1 through 1-15>>

Prepared Organic EL Elements 1-1 through 1-15 were evaluated. Table 1shows the results.

<<Evaluation of Organic EL Elements>>

The prepared Organic EL Elements 1-1 through 1-16 were evaluated asfollows. The non-light emitting surface of each of the organic ELelements was covered with a glass case, and a 300 μm thick glasssubstrate was employed as a sealing substrate. An epoxy based lightcurable type adhesive (LUXTRACK LC0629B produced by Toagosei Co., Ltd.)was employed in the periphery as a sealing material. The resulting onewas superimposed on the aforesaid cathode to be brought into closecontact with the aforesaid transparent support substrate, and curing andsealing were carried out via exposure of UV radiation onto the glasssubstrate side, whereby the illuminating device shown in FIGS. 3 and 4was formed, followed by evaluation.

FIG. 3 is a schematic view of the illuminating device and Organic ELElement 101 is covered with glass cover 102 (incidentally, sealing bythe glass cover was carried out in a globe box under nitrogen ambience(under an ambience of high purity nitrogen gas at a purity of at least99.999%) so that Organic EL Element 101 was not brought into contactwith atmosphere.

FIG. 4 is a cross-sectional view of a iilluminating device, and in FIG.4, 105 represents a cathode, 106 represents an organic EL layer, and 107represents a glass substrate fitted with a transparent electrode.Further, the interior of glass cover 102 is filled with nitrogen gas 108and water catching agent 109 is provided.

<<External Extraction Quantum Efficiency>>

Constant electric current of 2.5 mA/cm² was applied to the preparedorganic EL element at 23° C. under an ambience of desiccated nitrogengas, and the external extraction quantum efficiency (%) was determined.A spectroradiometric luminance meter CS-1000 (produced by Konica MinoltaInc.) was employed for the above determination.

The external extraction quantum efficiency in Table 1 was represented bythe relative value when the external extraction quantum efficiency ofOrganic EL Element 1-15 was 100.

<<Lifetime>>

When driven at a constant electric current of 2.5 mA/cm², the time whichwas required for a decease in one half of the luminance immediatelyafter the initiation of light emission (being the initial luminance) wasdetermined, and the resulting value was employed as an index of thelifetime in terms of a half lifetime (τ0.5). Meanwhile, aspectroradiometric luminance meter CS-1000 (produced by Konica MinoltaInc.) was employed for the above determination. Further, the lifetime inTable 1 is represented by a relative value when the lifetime of OrganicEL Element 1-1 was 100. Table 1 shows the results.

TABLE 1 External Organic EL Dopant Host Extraction Element Com- Com-Quantum Life- Re- No. pound pound Efficiency time marks 1-1 1-1 CBP 100100 Comp. 1-2 1-75 CBP 115 130 Comp. 1-3 1-77 CBP 90 120 Comp. 1-4 1-1 1130 160 Inv. 1-5 1-1 22 132 155 Inv. 1-6 1-1 29 128 150 Inv. 1-7 1-1 38126 153 Inv. 1-8 1-1 41 127 150 Inv. 1-9 1-75 1 145 250 Inv. 1-10 1-75 6140 230 Inv. 1-11 1-75 17 142 228 Inv. 1-12 1-75 22 141 230 Inv. 1-131-75 25 138 235 Inv. 1-14 1-75 27 136 231 Inv. 1-15 1-75 28 136 238 Inv.1-16 1-75 29 139 227 Inv. 1-17 1-75 38 140 228 Inv. 1-18 1-75 41 142 230Inv. 1-19 1-77 1 128 210 Inv. 1-20 1-77 22 125 202 Inv. 1-21 1-77 29 122209 Inv. 1-22 1-77 38 123 205 Inv. 1-23 1-77 41 129 200 Inv. Comp.:Comparative Example, Inv.: Present Invention

As can clearly be seen from Table 1, organic EL elements of the presentinvention achieved high efficiency and long lifetime, compared withcomparative examples.

Example 2

<<Preparation of Organic EL Element 2-1>>

Patterning was applied to a substrate (NA45 produced by NH Techno GlassCorp.) on which a 100 nm film of ITO (indium tin oxide) was formed, as aanode, on the above 100 mm×100 mm×1.1 mm glass substrate. Thereafter,the above transparent support substrate provided with the ITOtransparent electrode underwent ultrasonic washing with isopropylalcohol, dried via desiccated nitrogen gas, and underwent UV ozonewashing for 5 minutes.

The resulting transparent support substrate was fixed via the substrateholder of a commercial vacuum deposition apparatus. Separately, 200 mgof α-NPD was placed in a molybdenum resistance heating boat, 200 mg ofCBP as a host compound was placed in another molybdenum resistanceheating boat, 100 mg of Ir-1 was placed in further another molybdenumresistance heating boat, and 200 mg of Alg_(a) was placed in stillfurther another molybdenum resistance heating boat, and the resultingboats were fitted in the vacuum deposition apparatus.

Subsequently, after reducing the pressure of the vacuum tank to 4×10⁻⁴Pa, the aforesaid heating boat, in which α-NPD was placed, was heatedvia application of electric current and deposition was carried out ontothe transparent support substrate at a deposition rate of 0.1 nm/second,whereby a 40 nm thick positive hole transport layer was arranged.

Further, the aforesaid heating boats in which CBP and Ir-1 were placedrespectively, were heated via application of electric current, andco-deposition was carried out onto the aforesaid positive hole transportlayer at a deposition rate of 0.2 nm/second and 0.012 nm/second,respectively, whereby a 40 nm thick light emitting layer was arranged.The substrate during deposition had a room temperature.

Further, the aforesaid heating boat, in which BCP was placed, was heatedvia application of electric current and deposition was carried out ontothe aforesaid light emitting layer at a deposition rate of 0.1nm/second, whereby a 10 nm thick positive hole inhibition layer wasarranged.

Still further, the aforesaid heating boat, in which Alg₃ was placed, washeated via application of electric current, and deposition was carriedout onto the aforesaid positive hole inhibition layer at a depositionrate of 0.1 nm/second, whereby a 40 nm thick electron transport layerwas arranged.

Meanwhile, the substrate during deposition had a room temperature.

Subsequently, 0.5 nm lithium fluoride and 110 nm aluminum were depositedto form a cathode, whereby Organic EL Element 2-1 was prepared.

<<Preparation of Organic EL Elements 2-2 through 2-15>>

Organic EL Elements 2-2 through 2-15 were prepared in the same manner asOrganic EL Element 2-1, except that CBP which was the host compound inthe light emitting layer was replaced with each of the compounds listedin Table 2, and Ir-1 employed as a dopant compound in the light emittinglayer was replaced with each of the compounds listed in Table 2.

<<Evaluation of Organic EL Elements 2-1 through 2-28>>

Prepared Organic EL Elements 2-1 through 2-28 were evaluated in the samemanner as Example 1. Table 2 shows the results.

Meanwhile, in Table 2, each of the external extraction quantumefficiency and the lifetime is represented by a relative value when eachof the external extraction quantum efficiency and the lifetime ofOrganic EL Element 2-2 was 100. Table 2 shows the results.

TABLE 2 External Organic EL Dopant Host Extraction Element Com- Com-Quantum Life- Re- No. pound pound Efficiency time marks 2-1 Ir-1 CBP 100100 Comp. 2-2 1-83 CBP 103 105 Comp. 2-3 Ir-1 1 120 135 Inv. 2-4 1-83 1127 150 Inv. 2-5 Ir-1 22 113 124 Inv. 2-6 Ir-1 29 116 120 Inv. 2-7 Ir-138 118 119 Inv. 2-8 Ir-1 41 119 123 Inv. 2-9 1-83 22 120 148 Inv. 2-101-83 29 121 145 Inv. 2-11 1-83 38 122 148 Inv. 2-12 1-83 41 118 144 Inv.Comp.: Comparative Example, Inv.: Present Invention

As can clearly be seen from Table 2, organic EL elements of the presentinvention achieved high efficiency and long lifetime, compared withcomparative examples.

Example 3

<<Preparation of Full Color Display Device>>

(Preparation of Blue Light Emitting Element)

Organic EL element 1-9 of Example 1 was employed as a blue lightemitting element.

(Preparation of Green Light Emitting Element)

Organic EL element 2-4 of Example 2 was employed as a green lightemitting element.

(Preparation of Red Light Emitting Element)

A red light emitting element was prepared in the same manner as OrganicEL Element 1-1 in Example 1, except that the host compound was replacedwith CBP, and the dopant was replaced with Ir-14. The resulting elementwas employed as a red light emitting element.

The red, green, and blue light emitting organic EL elements, prepared asabove, were arranged parallel on one substrate, and an active matrixsystem full-color display device which had the configuration, shown inFIG. 1, was prepared. In FIG. 2, shown is a schematic view of displaysection A of the above prepared display device.

Namely, on one substrate, arranged is a wiring section incorporating aplurality of scanning lines 5 and data lines 6, and a plurality ofparallel pixels 3 (pixels in the red light emitting region, pixels inthe green light emitting region, and pixels in the blue light emittingregion), and each of scanning lines 5 and a plurality of data lines 6 ofthe wiring section is composed of electrically conductive materials.Scanning lines 5 and data lines 6 are orthogonalized in a reticularpattern and connect to pixels 3 in each of the orthogonalized positions(not shown in detail).

The aforesaid plurality of pixels 3 is driven via an active matrixsystem provided with an organic EL element corresponding to each of theemitted light colors and each of the switching transistors and the drivetransistors. When scanning signals are transmitted from scanning lines5, image data signals are received from data lines 6, and light emissionoccurs depending on the received image data.

By appropriately arranging parallel red, green, and blue pixels, afull-color display device was prepared.

By driving the above full-color device, it was noted that sharpfull-color images with high luminance and high durability were prepared.

Example 4

<<Preparation of White Light Emitting Element and White LightIlluminating Device>>

The electrode of the transparent electrode substrate underwentpatterning in an area of 20 mm×20 mm, and, a 40 nm thick α-NPD film wasformed thereon as a positive hole injection/transport layer in the samemanner as Example 1. Further, eclectic current was independently appliedto each of the aforesaid heating boat in which Exemplified Compound Iwas placed, the boat in which Exemplified Compound I-75 was placed, andthe boat in which Ir-4 was placed, and vapor deposition was carried outto result in a film thickness of 30 nm, while regulating the vapordeposition rate to 100:5:0.6, respectively, whereby a light emittinglayer was arranged.

Subsequently, a 10 nm BCP film was formed, whereby a positive holeinhibition layer was arranged. Further, a 40 nm Alq_(a) film was formed,whereby an electron transport layer was arranged.

Subsequently, in the same manner as Example 1, square shaped perforatedstainless steel mask having the almost same shape as the transparentelectrode was arranged on the electron transport layer, and a 0.5 nmlithium fluoride film as a cathode buffer layer and a 150 nm aluminumfilm as a cathode were formed via vapor deposition.

By employing the resulting element, a flat lamp having a sealedstructure similar to that in Example 1 was prepared in the same manneras Example 1. When electric current was applied to the resulting flatlamp, it emitted nearly white light, whereby it was noted that it wasusable as an illuminating device.

The invention claimed is:
 1. An organic electroluminescent elementcomprising a substrate having thereon at least an anode and a cathode,and a light emitting layer between the aforesaid anode and the aforesaidcathode, wherein at least one light emitting layer incorporates acompound represented by Formula (A):

wherein A1 represents a nitrogen-atom containing substituent and A2represents a hydrogen atom or a substituent; X and Y each represents;L1, L2, and L3 each represents a divalent linking group; n represents aninteger of 1 or more; n1 and n2 each represents an integer of 1 or more;and n3 and n4 each represents an integer of 0 or 1, provided that thefollowing condition is satisfied, n1 +n2≧2.
 2. The organicelectroluminescent element of claim 1, wherein the aforesaid L3represents an arylene group, a heteroarylene group, a divalentheterocyclic group or an alkylene group.
 3. The organicelectroluminescent element of claim 1, wherein the aforesaid L3represents an arylene group.
 4. The organic electroluminescent elementof claim 1, wherein the aforesaid L3 represents a m-phenylene group. 5.The organic electroluminescent element of claim 1, wherein the aforesaidn1 represents 1 or
 2. 6. The organic electroluminescent element of claim1, wherein the aforesaid n2 represents 1 or
 2. 7. The organicelectroluminescent element of claim 1, wherein the aforesaid nrepresents 1 or
 2. 8. The organic electroluminescent element of claim 1,wherein the aforesaid nitrogen atom-containing substituent is acarbazolyl group.
 9. The organic electroluminescent element of claim 1,wherein the aforesaid nitrogen atom-containing substituent represents acarbolinyl group and the aforesaid carbolinyl group is the substituentwhich is derived from the carboline derivative represented by Formula(a):

wherein X₁-X₈ each represents a nitrogen atom or —C(Ra)═; at least oneof the aforesaid X₁-X₈ represents a nitrogen atom; and Ra and Rb eachrepresents a hydrogen atom or a substituent.
 10. The organicelectroluminescent element of claim 1, wherein the aforesaid nitrogenatom-containing substituent is a diarylamino group.
 11. The organicelectroluminescent element of claim 1, wherein the aforesaid lightemitting layer incorporates a phosphorescence emitting metal complex.12. The organic electroluminescent element of claim 11, wherein theaforesaid phosphorescence emitting metal complex is an Ir complex. 13.The organic electroluminescent element of claim 11, wherein theaforesaid phosphorescence emitting metal complex is represented byFormula (B):

wherein R₁ represents a substituent; Z represents a group of metal atomsnecessary for forming a 5-7 membered ring; n₁ represents an integer of0-5; B₁-B₅ each represents a carbon atom, a nitrogen atom, an oxygenatom, or a sulfur atom and at least one represents a nitrogen atom; M₁represents a metal of Groups 8-10 in the element periodic table; X₁ andX₂ each represents a carbon atom, a nitrogen atom, or an oxygen atom; L₁represents a group of atoms which form a bidentate ligand with X₁ andX₂; m1 represents 1, 2, or 3; and m2 represents 0, 1, or 2, providedthat a sum of m1 and m2 is 2 or
 3. 14. The organic electroluminescentelement of claim 1, wherein m2 of the phosphorescence emitting metalcomplex represented by the aforesaid Formula (B) is
 0. 15. The organicelectroluminescent element of claim 13, wherein a nitrogen-containingheterocyclic ring formed by phosphorescence emitting metal complexesB1-B5 represented by the aforesaid Formula (B) is an imidazole ring. 16.The organic electroluminescent element of claim 1, emitting white light.17. A display device provided with the organic electroluminescentelement of claim
 1. 18. An illuminating device provided with the organicelectroluminescent element of claim 1.